Electric induction heating apparatus



p 1953 J. c. HOWARD 2,652,478

ELECTRIC INDUCTION HEATING APPARATUS Filed Jan. 5, 1950 Inventor JOHNCumsn: How/mo Attorney Patented p 15.1953

I ELECTRIC INDUCTION HEATING APPARATUS John Christie Howard, Weybridge,England, as-

signor to The Ohio Crankshaft Company; Cleveland, Ohio, a corporation ofOhio Application January 5, 1950, Serial No. 137,000 In Great BritainJanuary 7, 1949 1 Claim.

This invention relates toelectric induction heating apparatus for heattreatment of metallic strip progressively.

There are a number of forms of inductor suitable for heating a workpiecein strip form, which act asymmetrically on the workpiece, for example ononly one side of it. That known as the pancake type comprises a flatspiral coil; that known as the hairpin or loop type comprises a singleturn or multiple turns of elongated shape; whilst various forms of ironcored inductor are available employing a single turn or a number ofturns associated with a laminated or powder core of magnetic material toconcentrate the flux. All types of inductors when energised andpresented to one side of the workpiece set up mechanical forces whichtend to move the strip towards, or away from, the inductor, depending onwhether the workpiece is magnetic or not. In order to maintain aconstant heat input to a workpiece in strip form, and hence a constanttemperature, it is essential to maintain constant the relative positionbetween the strip and the inductor. Moreover in many cases it isimportant not to impair the surface finish of the strip, and this rulesout the use of guides through which the strip rubs, since these wouldtend to scratch and spoil the surface.

It is therefore an object of the invention to provide means for the heattreatment of metallic strip by electric induction heating in which therelative position of the inductor and strip is kept constant withoutscratching the surface of the strip.

According to the present invention electric induction heating apparatusfor heat treatment of metallic strip includes a locating roller round aportion of the circumference of which the strip is wrapped, an inductoracting on that side of the strip remote from the roller, and means forkeeping the strip in tension as it is advanced. The inductor may be ofany of the forms referred to above, but is preferably suitably curved toconform to the curvature of the strip as it passes round the locatingroller.

The invention may be carried into practice in various ways, but onespecific embodiment will now be described by way of example withreference to the accompanying drawing, which represents diagrammaticallyin side elevation electric induction heating apparatus for the heattreatment of metal strip.

In this embodiment the strip II] is fed from a supply roll II, under aguide roller I2, over a locating roller l3, and under a second guide 2roller M to a take-up roller [5. The relative position of the locatingroller I3 and the two uide rollers l2 and I4 is such that the strip I0is wrapped round anything up to about half the circumference of thelocating roller. The strip II is kept in tension by winding mechanismacting on the take-up roll l5 and supply roll ll, thereby holding itfirmly in contact withthe locating roller 1 3, which rotates freely. Aninductor l6 acts upon the side of the strip [0 remote from the locatingroller 13. The inductor I6 is of laminated cored type with the windingll wound in sinuous form around teeth l8 in the stack of laminations.The core is curved so as to conform to the curvature of the strip In asit approaches, passes round and recedes from the locating roller l3. Inthe construction shown in the drawing, in which the strip l0 passesround half the circumference of the locating roller [3, the core is ofsemi-cylindrical shape as shown.

The construction of the locating roller i3 may vary but in thisembodiment it comprises a refractory drum [9 mounted on a steel spindle20 and covered with a smooth heat-resisting metal tube 2|. In this casethe heat resisting tube 2| will be heated by induction and heat will beconducted from it to the strip I0, thus supplementingllthe heat producedby induction in the strip 1 se The apparatus may be employed forcontinuous hardening and tempering of steel strip or sheet or forannealing of ferrous or non-ferrous strip. Moreover, it may be enclosedin a gas-tight chamber to provide an inert atmosphere for bright heattreatment.

What I claim as my invention and desire to secure by Letters Patent is:

In apparatus for heating continuous lengths of moving metallic stripincluding a rotatably mounted drum over which the strip to be heated isadapted to pass and having an axis of r0- tation, a high-frequencyinductor in operative relationship with said drum and said strip on oneside of said axis and a pair of other rotatably mounted drums underwhich the strip to be heated is adapted to be passed and each having anaxis of rotation, the axes of rotation of said other drums beingpositioned on a side of the axis of rotation of said first mentioneddrum opposite from that of said inductor, said inductor having anarcuate concave surface having a center of curvature approximating thatof the axis of rotation of said drum, the arcuate face of the inductorbeing in slightly spaced relationship with the surface of said drum, theimprovea a ment which comprises said drum being comprised of an outersteel shell mounted on a ceramic insulating inner member, said outershell being inductively heated by the high-frequency inductor toelevated temperatures where by to assist in the transfer of heat to thestrip by both, conduction and radiation.

JOHN CHRISTIE HOWARD.

Number Name Date Frary May 10, 1921 Number Numlber Name Date NorthrupApr. 16, 1935 Wilson May 23, 1944 Denneen et a1 Jan. 14, 1947 WilsonSept. 16, 1947 Baker et a1 Aug. 31, 1948 King Nov. 2, 1948 Lee Dec. 21,1948 Gehr et a1. Aug. 16, 1949 FOREIGN PATENTS Country Date GreatBritain Dec. 24, 1924

